GB2322527A

GB2322527A - Data error correction

Info

Publication number: GB2322527A
Application number: GB9725840A
Authority: GB
Inventors: Dong-Seek Park
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1997-02-24
Filing date: 1997-12-08
Publication date: 1998-08-26
Anticipated expiration: 2017-12-08
Also published as: DE19755372C2; GB9725840D0; JPH10322227A; DE19755372A1; KR100224868B1; GB2322527B; KR19980069911A; CN1211121A

Abstract

A data error correcting method determines the range of data error correction to minimize the elimination of error-free data by minimizing the range for correcting data errors generated during decoding of received data. The steps include (a) detecting an error in data during forward decoding; (b) determining the location of a forward error block which corresponds the location of the first predetermined unit data block including error data detected in step (a); (c) stopping forward decoding and detecting an error in data while decoding the data in a reverse direction, if an error is detected in said step (a); (d) determining the location of a reverse error block which corresponds to the location of the data block including the error detected in said step (c); and (e) determining the data between said forward and backward error blocks, inclusive, as an error correction range. Therefore, high-quality reproduction can be achieved by minimizing an error correction range by means of reverse decoding and thus reducing elimination of error-free data, eg for multimedia video data.

Description

2322527 METHOD FOR DETERMINING RANGE OF DATA ERROR CORRECTION The present

invention relates to a data error correcting method. More particularly, the present invention relates to a method for determining the range of data error correction to minimize the elimination of normal data by minimizing the range of correcting data errors generated during decoding of received data.

In general, errors are unavoidably included in data received by a portable telephone in a metropolitan area or by communication satellites in bad weather. A method for correcting these errors significantly influences the data processing speed of communications.

There are typically two error data correcting methods. The first method repeatedly re-transmits data which may contain errors between a decoder and an encoder until no errors are detected. This method rapidly reduces the processing capability that may be realized in a communications channel. The extent of the reduction in processing capability is closely related to the frequency of the re-transmissions.

The second method discards the data of a group of blocks (GOB) which includes a macro block (MB) in which errors are detected. The data of the same GOB of a previous frame is further processed in place of the discarded data. An example of this error correction is that of a video data processor.

As shown in Figure 3, if an error is detected when decoding a sixth MB in GOB 2 of an Nth frame, a decoder stops decoding until the next GOB synchronization signal is f ound. If the synchronization signal of GOB 3 is found, all the data of the current GOB 2 of the Nth frame is discarded, and the data of GOB 2 in frame N-1 is copied in the area of GOB 2 in the Nth f rame. However, if the next GOB synchronization signal which is found corresponds to GOB 5, all the data of GOBs 2, 3, and 4 of the Nth f rame are discarded and the data of GOBs 2, 3, and 4 in the (N-1)th frame are copied in the areas of GOBs 2, 3, and 4 in the Nth frame. The second conventional method has the disadvantage of discarding a large amount of data which is error-free.

The above conventional error correcting methods have deficiencies which rapidly reduces the processing capability that may be realized in a communications channel, or discards a large amount of normal data.

It is an aim of embodiments of the present invention to provide a method for determining the range of data error correction, which minimizes the amount of error-free data that is discarded during data correction.

According to an aspect of the invention, there is provided a method for determining a range of data err gr correction during decoding of a first predetermined unit data block and a second predetermined unit data block constituted by a set of the first predetermined unit data blocks, said method comprising: (a) detecting an error in data of said first predetermined data blocks during forward decoding; (b) determining the location of a forward error block which corresponds to the location of the first predetermined unit data block including error data detected in step (a); (c) stopping said f orward decoding and detecting an error in data while backward decoding the first predetermined unit data blocks of the second predetermined unit data block, said backward decoding being performed from a last position towards a first position of said first predetermined unit data blocks in said second predetermined unit data block if an error is detected in said step (a); (d) determining a location of a reverse error block which corresponds to the location of the first predetermined unit data block including error data detected in said step (c); and (e) designating the data between said forward and backward error blocks, inclusive, as an error correction range.

Preferably, said first predetermined unit is a minimum unit data error determining block.

According to a second aspect of the invention, there is provided a method of determining a range for data error correction for data arranged in a first unit data block and a second unit data block, said second unit data block including a set of the first unit data blocks arranged from a first position to a last position, said method comprising: (a) performing forward decoding on the first unit data blocks beginning from the first position; (b) determining whether an error occurs in the data during said forward decoding; (c) determining a location of - a forward error block which corresponds to the location of the first unit data block including the error which occurred in step (b); (d) stopping said forward decoding and performing backward decoding on said data, said backward decoding being performed from the last position of said first unit data blocks in said second predetermined unit data block if an error is detected in said step (b); (e) determining whether an error occurs in the data during said backward decoding; (f) determining a location of a reverse error block which corresponds to the location of the first predetermined unit data block including the error which occurred in said step (e); and (g) designating the data between said forward and backward error blocks, inclusive, as an error correction range.

Said first unit data block is preferably a minimum 5 unit data error determining block.

The method may further comprise: performing error correction on said error correction range.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 is a flowchart of a method for determining the range of data error correction according to an aspect of the present invention; Figures 2A through 2C illustrate several forms of error correction ranges determined according to the method of the present invention; and method.

Figure 3 illustrates a conventional error correcting Referring to Figure 1, a method for determining the range of data error correction includes the steps of decoding data in a forward direction (step 110), making a first determination of whether an error is found in the data during forward decoding (step 120), detecting the location of a first macro block including the data having an error detected during the forward decoding (step 130), shifting a macro block position being decoded to the last macro block position of a current GOB (step 140), decoding data in a reverse direction (step 150), making a second determination of whether an error is found in the reverse decoded data (step 160), detecting the position of a second macro block including the data having an error detected during the reverse decoding (step 170), determining the data between the first and second macro blocks to be the range of error correction (step 180), and correcting the data in the error correcting range (step 190). The error correction for the range may be performed using known techniques.

The above steps will be described, taking multimedia video data processing as an example. Because the decoding of received communications data is well-known, the details of the decoding will not be provided. The decoding may be performed on any sub-unit of a block of data.

In multimedia video data, a minimum unit set of data for processing data such as a video signal is termed a block, a predetermined number of blocks constitute a macro block, a predetermined number of macro blocks constitute a group of blocks (GOB), and a predetermined number of GOBs constitute a frame.

In step 110, compressed video data is decoded in a forward direction. For example, the data of macro blocks in a GOB is decoded in the order in which the macro blocks are located.

In step 120, it is determined whether an error is found during the forward decoding, that is, whether a syntax error is generated during decoding of the data. If it is determined that an error exists, the forward decoding is stopped, and subsequent procedures, as described below, are performed.

In step 130, when an error is found in step 120, the location of a first macro block including data having the error is determined.

In step 140, when an error is detected in step 120, the position of the data to be decoded is shifted to the last macro block in a current GOB which is undergoing the decoding process.

In step 150, macro blocks are sequentially decoded in descending order from the last to first macro block of the GOB. That is, reverse decoding is performed in the reverse order in which the macro blocks are located from the lowest label of syntax with reference to entropy and syntax tables, in the case of the H.263 standard.

In step 160, it is determined whether an error is generated during reverse decoding, that is, whether a syntax error is generated during decoding of the data in the reverse direction. If it is determined that an error is generated, the reverse decoding is stopped.

In_step 170, the location of a second macro block including data having the error generated in step 160 is detected.

In step 180, as shown in FIGs. 2A through 2C, the block data between the first macro block having the detected forward decoding error (f.e.) and the second 30 macro block having the detected backward decoding error (b. e.), including the first and second macro blocks, is determined as the range of error correction.

FIGs. 2A through 2C illustrate examples of error correction ranges corresponding to detected errors in forward and backward decoding. In FIGs. 2A and 2B, the data of the blocks determined to contain errors during the forward and backward decoding and the blocks between the macro blocks having forward and backward decoding errors is determined as an error correction range. In Figure 2C, a single macro block is determined as an error correction range since forward and backward decoding errors occur in the same macro block position.

In step 190, the data between the first and second macro blocks determined as the error correction range of a frame currently being decoded is discarded, and the macro block data between the first and second macro blocks, inclusive, of a previous frame is copied into the discarded data position.

Through the above procedure, the present invention can minimize the amount of data discarded due to error generation.

As described above, the present invention can effect high-quality reproduction in the case of video data processing by minimizing an error correction range by means of reverse decoding and thus reducing elimination of normal data.

Though the present invention has been described referring to multimedia video data processing as an example, the present invention is not limited thereto.

Thus, it is clearly understood that the present invention can be applied to all digital data error correction fields.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to - 8 this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

- 9 is

Claims

1. A method for determining the range of data error correction during decoding of a first predetermined unit data block and a second predetermined unit data block including a set of the first predetermined unit data blocks, said method comprising:

(a) detecting an error in data of said first predetermined data blocks during forward decoding; (b) determining a location of a forward error block which corresponds to the location of the first predetermined unit data block including the error data detected in step (a); (c) stopping said forward decoding and detecting an error in data while backward decoding the first predetermined unit data blocks of the second predetermined unit data block, said backward decoding being performed from a last position towards a first position of said first predetermined unit data blocks in said second predetermined unit data block if an error is detected in said step (a); (d) determining a location of a reverse error block which corresponds to the location of the first predetermined unit data block including error data detected in said step (c); and (e) designating the data between said forward and backward error blocks, inclusive, as an error correction range.

2. The method for determining the range of data error correction as claimed in claim 1, wherein said first - 10 predetermined unit is a minimum unit data error determining block.

3. A method of determining a range for data error correction for data arranged in a first unit data block and a second unit data block, said second unit data block including a set of the first unit data blocks arranged from a first position to a last position, said method comprising:

(a) performing forward decoding on the first unit data blocks beginning from the first position; (b) determining whether an error occurs in the data during said forward decoding; (c) determining a location of a forward error block which corresponds to the location of the first unit data block including the error which occurred in step (b); (d) stopping said forward decoding and performing backward decoding on said data, said backward decoding being performed from the last position of said first.unit data blocks in said second predetermined unit data block if an error is detected in said step (b); (e) determining whether an error occurs in the data during said backward decoding; (f) determining a location of a reverse error block which corresponds to the location Of the first predetermined unit data block including the error which occurred in said step (e); and (g) designating the data between said forward and backward error blocks, inclusive, as an error correction range.

4. The method of determining the range for data error correction as claimed in claim 3, wherein said first unit data block is a minimum unit data error determining block.

5. The method of claim 3 or 4 further comprising:

performing error correction on said error correction range.

6. A method for determining a range for data error correction, substantially as hereindescribed with reference to Figures 1 and 2.

is